In general, there are two electronic document encrypting methods. In the first electronic document encrypting method, an access right for a document is set, and in the second electronic document encrypting method, the document is itself encrypted. In the first electronic document encrypting method, a password for authenticating an access right is stored in a header portion of a document, and whether a password input from a computer terminal is identical to the stored password is determined when the document is opened via an editor such as a word processor. When the input password is identical to the stored password, the document is opened. When the input password is not identical to the stored password, the document cannot be opened. The first electronic document encrypting method may be simply implemented. However, the first electronic document encrypting method has low security because the content of the document may be simply read by using a hacking tool when the password is not known.
The second electronic document encrypting method has high security because the content of the document is encrypted. However, it takes a considerable time to decrypt a large document using the second electronic document encrypting method. Also, if the password is forgotten or lost, there is a risk that the document may not be recoverable. Document encryption may be performed by an editor such as a word processor, and a separate utility program is widely used to encrypt a document file.
Since the related art electronic document encryption is applied to an entire document, this encryption is inefficient when encryption of only some area of the document is necessary. Also, since the entire document is encrypted, it takes considerable time to decrypt the encrypted document.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.